Process for separating phenols



Jan. 2', 1945.

D. B. LUTEN, JR., x-:jrAL

, PROCESS FOR SEPARATING PHENOLS Filed June 2, 1942 /m/nrors. Danie/ B. Lure/7, J7:

- H/do De Benedic/' Passau Jan. 2, 1945 PATENT* FFICE PROCESS FOR SEPARATING PHENOLS Daniel B. Luten, Jr.,

na Aldo ne Benedicta,

Berkeley, Calif., assignors to Shell Development Company, San Francisco, Calif., a'corporation `of Delaware Application June 2, 1942, LSerial No. 445,512

4 claims. (ci. 26o-teli 'I'he present invention relates to a process for separating phenols from other phenols normally associated therewith in mixtures derivedl from separation by distillation very dimcult or even impossible. f` In the past it has been proposed to separate mixtures of phenols by a method comprising sulfonating the mixture under conditions to form a mixture of the corresponding phenol sulfonic Vacids and then treating the resulting sulfonation product with a solution of a basic potassium, sodium or barium compound under conditions to neutralize the productfand form the corresponde ing salts of the various phenol sulfonic acids. The salts of the various different phenol sulfonicacids thus formed sometimes exhibit differences/in solubility, which property may be utilized to effect their separation.

It is an object of our invention to provide an improved method for separating phenols. It is another object to provide a process which permits regeneration of the reagents employed torre-use in treating further quantities of phenols to be separated either in batch or continuous processes. -Further objects of our invention will be evident from the following.

Our invention comprises sulfonating a mixture of phenols to be separated with an excess of sulmaining phenol sulfonic acids remain in solution. The -two phases then formed are separated, and

separately subjected' to hydrolysis for the re covery of the phenols from their saltsin purified form, thus regenerating the sulfates and sulfuric acid, which are recycled totheprocess to treat further quantities of phenols to be separated, as

'hereinafter more fully described; n Our invention may better understood from a consideration of the'lgure, which represents al schematic ow diagram of this process. Forg' simplicity of description, the 'alkyl phenol mixture treated is exempliiled'by a specic x'ylenol mixture.' s

v An a1ky1 p henn feed manure having an ASTM boiling range between 190 and 220 C., and containing 2,4 4and 2,5-dimethyl phenols along with minor quantities of impurities (for example, an alkyl phenol fraction prepared by distilling a relatively wide boiling range alkyl phenol mixture, which latter was extracted from a cracked petroleum distillate by means 'of caustic alkali and recovered therefrom by springing with carbon dioxide) is fed via line" I to reactor 2. Herein the phenolic mixture is contacted with a slurry of concentrated sulfuric acid and potassium acid sulfate admitted to reactdr 2 via line 3. Reactor 2 is maintained at an elevated temperature, e. g. between about 40 and 120 C. depending on the concentration of sulfuric acid employed; the more concentrated the acid the lower thetemperature required. The quantity of sulfuric acid is ad- J'usted so that an excess of sulfuric acid over the stoichiometric equivalent of the phenols is present. Under these conditions substantially all of the alkyl phenols are'converted primarily to the corresponding monosulfonic acids. -The potassium acid` sulfate admitted with the concentrated acid is largely insoluble and the soluble portion is substantially inertl under y,these conditions. After the monosulfonic acids have formed, water is -added to reactor 2 via valved'line 4 in such an`-amount that the potassium acid sulfate dissolves and ionizes and potassium salts of the 30 phenol sulfonic acids are formed which partially gointo solution. The quantity of water is so regulated that the resulting solution has a concentration of approximately- 15%` free sulfuric acid. This concentration of acid forthis particular operation affords excellent separation of the potassium salts of 2,4- and 2,5-dirnethyl phenol sulfonic acids, the potassium salt `ci.' 2,4- vdimethyl phenohs'eparating asia solid while the ypotassium 2,5-dimethy1 phenol sulfonate largely remains in the mother liquor. Thel resulting mixture, preferably after cooling, is passed via line 5 to lter 6 to separate the solid from the mother liquor. A K e s The liquid illtrateis -passed via line''l to boiler 45 8. Water or concentrated acid ,may be added via valved line 9 to adjust the ,concentration of the filtrate to favor hydrolyslsjin boiler 8; or, ii desired, water may be removed by preliminary distillation from boiler 8 to adjust the concentra- 50 tion. For this particular separation, a concentration of between` about 20and 60% sulfuric .acid affords a good hydrolytic medium. Upon p heating, the potassium 2,5-dimethyl'pheno1 suli 'fonate is hydrolyzed whereby 2,5-dimethyl phenol 55 and 4potassium acid sulfate are regenerated ,and

, the former is distilled overhead together with steam via line and condenser I to phase separator II. Up'on condensation, water phase `is withdrawn via line I3 while the phenol phase is withdrawn via line I2, passing to storage not shown. Residual sulfuric acid and acid sulfate are returned through lines I4, 21 and 3 to reactor 2.

The solid potassium 2,4-dimethyl phenol sulfonate from illter 6 is passed via conduit I5 to boiler I 6. An aqueous sulfuric acid solution of about 50% concentration is added to the potasn the potassium 2,4-dimethyl phenol sulfonates` takes place to regenerate the 2,4-dimethyl phenol and potassium acid sulfate. In the second place, potassium acid sulfate exhibits a low solubility in acid of this strength. r. y

In the course of the hydrolysis brought about by boiling in boiler I8, potassium acid sulfate is regenerated and is withdrawn via line and cooler 2 I, along withaqueous sulfuric acid solution, passing to lter 22. Solid potassium acid sulfate which has been precipitated is separated from the remaining sulfuric acid-solution. The solid potassium acid sulfate is passedback to reactor 2 via conduits 23, 21 and 3, after being mixed with the slurry emanating from boiler 8 via line I4. The ltrate from filter 22 is recycled to boiler I6 via lines 24 and I5 to hydrolyze further quantities of potassium 2,4-dimethyl phenol sulfonate. If desired, ltrate may be discarded through line 26 and fresh sulfuric acid of about 50% concentration introduced through line 25.

The regenerated 2,4-dimethyl phenol'emerges from boiler I6 with steam through line and .con'

denser I1. Upon condensation, water and phenol phases are separated in separator I8, the former being withdrawn via line I9, while the latter is about 5 and.50%.

tures between 0 and 150 C. or preferably between room temperature and 100 1C. In general, the ratio of sulfuric acid to phenols should be between about 0.5 and 2 parts by weight of sulfuric .acid per part of phenols, preferably with about equal parts of acid and pli no1. Excess acid tends to shift .the sulfonation ecxlumbrium in the desired direction ofA complete sulfonation, and at the same time may conveniently be adjusted to result in an acidity favorable to the separation of the phenol sulfonic acid salts after the addition of the sulfate solution in the subsequent treating step. Too large an excess of very strong (e. g. fuming) sulfuric acid will result in polysulfonation. However, under the above conditions mono- 'sulfonation occurs almost completely to the exclusion of polysulfonation.

After the phenols are sulfonated the mixture is treated with an aqueous Isolution of a sulfate or acid sulfate of lithium, sodium. potassium, ammonium or magnesium. It is convenient to employ these sulfate or acid sulfate solutions in amounts ranging from about stoichiometrically equivalent quantities of the phenolsulfonic acids present to excesses of the order of 400%, in-such concentration that the resulting mixture will have a vfree sulfuric acid concentration of between Ordinarily good separation of the salts of the phenol sulfonic acid occurs in solutions of this concentration-although other concentrations may be desirable in special cases. In carrying out the hydrolysis of the solid salts optimum acid concentration depends primarily withdrawn v ia line 20, passing to storage not .skilled in the' art; e. g., the process may be readily carried out either as a, batch, continuous orl semi-continuous process by the addition of ap- "propriate time tanks andA other equipment re- .quired for such purposes.

Likewise, it may be desired to separate the l phenols regenerated by hydrolysis in'boilers 8 or I8 by solvent extraction with a substantially Water-immisciblesolvent, such as benzene, hydro-` carbon fractions, etc., instead of recovering the phenols by steam distillation as indicated.'

It may be desirable to carry out the hydrolysisv upon the solubility of the particular salt that is regenerated in the course of the hydrolysis. In the case where potassium acid sulfate is the salt utilized and regenerated, 'a concentration of about 50%' sulfuric acid is optimumbecause as mentioned before the potassium acid sulfate exhibits a minimum solubility at thisconcentration, which permits it to be readily separated by ltration or centrifuging so that the acid may be employed repeatedly in the hydrolysis of subsequent quantities of solid salts of the phenol sulfonic acids without carrying an excessive amou'nt of salt in solution from cycle to cycle.

In the hydrolysis of the soluble salts of the phenol sulfonic acids contained in the mother s liquor, the above consideration is not important since the acid must be concentrated in any case before re-use as a sulfonating. agent, andthe presence of potassium acid salt makes little dif-l ference, in cases where the handling of a slurry oiers no difficulty. In case it is desired to separate the salt regenerated upon hydrolysis after the phenols are liberated and removed, it is convenient to concentrate the residual solution to a point corresponding to minimum solubility for the salt in question, .followedt'then by the separation by heating under pressure, although ordinary' boilingV is usually preferred,- since simultaneously the acid is concentrated and the phenols are removed along with the steam` With regard to the specific conditions. as to temperature, concentration, etc., in the various generally since they depend upon the particular system under consideration, i. e. the particular alkyl phenols to be separated, the anion employed in the acid sulfate, etc. In generaL it may be said the sulfonation should' be carried out with relatively concentrated sulfuric acid (i. e. 'l0--100%)` at temperaof the salt from the residual liquor and. further concentrating the resulting mother liquor in the absence of the salt 'to result in acid of sulfonation strength. Since most sulfates go through solubility minima at some concentrations between about 10% and 90%, generally the concentrated 'steps of the process, itis impossible to state these handling a slurry may then be avoided. The acid free from solids and solid salt so obtained may then be used separately to treat further quantinarrow boiling range mixture.

4broader fractions' may b treated, usually at a Yto employ a sulfate ofsodium,

1 'ascuas In this casey the sulfuric acid eflluent is normally split'into two portions, one passing to conceni trator 3l yfor further concentration while the other is recycled to line I5 to hydrolyze further quantities of solid sulionate.

In the ow diagraml shown in the drawing fresh sulfuric acid and sulfate may be introduced at any of several points (not identified) which may be, chosen to suit convenience. Likewise. acid or salt may be withdrawn at other points.

In general, our process is applicable to the separation of any phenolic mixture containing a plurality of phenols, the sodium, potassium, lithium, ammonium or magnesium salts of sulfonic'acids of which exhibit appreciable differences in solubility in aqueous sulfuric acid solutions.

When it is desired to isolate 'pure phenols it is usuallydesirable'to start Jwith a relatively In general, for this purpose the mixture treated should not contain more vthan one phenol whose corresponding sulfonic acid salt will precipitate under the conditions 'ofthe process, although somewhat sacrifice of oproduct purity. For example, if it is desired-to separate `2,4--dimethy1 phenol by our process inv a pure condition employing po-` tassium acid sulfateI it is desirable lthat the phenolic fractionshould be substantially free from para-cresci, 2-methyl' 4-ethyl phenol, 2,3,6- trimethyl ,phenol or i other higher molecular weight phenols, the potassium salts of the corresponding sulfonic acids of which tend to separate along with the potassium. salt of ,2A-dimethyl phenol sulfonic acid.

It is evident that our process `may sometimes be utilized serially to reduce lmulti-component phenolic mix-tures to simpler constituent groups by first treating such a mixtureto separate primary and secondary multi-component mixtures of lesser complexity, one orboth of which components lmay be subjected to further treatment, preferably under slightly alteredconditions of concentration or with some other sulfate thanthe one initially employed. By repetition of this furnished by potassium acetate, yin which case the acetic 'acid formed would be removed with the first phenols produced and in'subsequent cycles only potassium acid sulfate would be recirculated to the process.

Although any salt of the type vdescribed m .be employed. we in general prefergto employ sulfates 4oi? sodium or potassium,v and particularly their acid sulfates. l i

We claim as our invention: v .i 1. VA process for separating 2,4 and 2,5-di'- methy1 phenols from a mixture containing them comprisingthe steps of Atreating said mixture with sulfuric acid under conditions to convert said phenols predominantly to the corresponding phenol monosulfonic acids, adding to the resulting mixed sulfonated phenols containing a substantial amount of free sulfuric acid an aqueous solution of water-soluble electrolytes of a cation selected from the group consisting of potassium,

sodium, lithium, ammonium, and

magnesium in an amount between about 100% Vof the 2,5-dimethyl phenol sulfonic acid, sulfuric acid 'and water, separating said phases, subject- Y methyl'phenol sulfonic acid and the othea a process relatively wide boiling range mixtures can frequently be reduced to simplified mixtures Lis not necessary potassium, lithium,v ammonium or magnesium4 for the firstcycle. 1, Any lwater-soluble ,electrolyte includingorganic salts (e. g. potassium acetate, formate. etc.) which furnish the proper cation maybe employed.y lAfteiv the nistncycle the cation will .be regeneratedas a lsulfate of the metal while the anions may be withdrawn fwith the proding the phenol Ysulfonic acid salt of atleast one of said phases to conditions to result in the hydrolysis of the phenol sulfonate contained therein to regenerate the corresponding phenol and to form a sulfate of said cation, separating said regenerated phenol from said sulfate and recycling the latter to treat further quantities of said mixed phenol sulfonic acids.

2. A process for separating r2,4-and 2,5-dimethy1 phenols from a mixture containing them comprising the steps of treating said' mixture with sulfuric acid under conditions to convert said phenols predominantly to the corresponding pheno1 monosulfonic acids, adding to the resulting mixed sulfonated phenols containing a substantial amount of free sulfuric acid an aqueous solution of water-soluble electrolytes of a-cation..

selected from the group consisting of potassium,

sodium, lithium,`ammonium, and magnesium 'in`l I an amount between about 100% and 400% of the stoichiometrical quantity of said 'mixed sulfonated phenols and .undenconditions to form two phases, one being a solid consisting essentially of the lesssoluble Asalt of the said 2,4-d1- mother liquor containing the more soluble salt of the ri-dimethyl phenol sulfonic acid, sulfuric acidandfwater, separating saidvphases, subjecting" the phenol sulfonic acid saltof at leastone of said phases to conditions to result in thehydrolysis of the phenol sulfonate contained there- A in to regenerate the corresponding phenol and ucts. or'be lallowed tol circulate in the system.

to form a sulfate of said lcationfand separating said regenerated phenal from said sulfate.

3. The process of 'c1aim2 wherein said regenerated phenolsy are. separated from the hydrolyzed mixture by steam distillation.

4. The lprocess of'claim 2.wherein said sulfate is potassium acid sulfate.

DANIEL-B. LUTEN', Ja. ALDO DE BENEDICTIS.

For example, if desired, the potassium ion can be'l 

